I disagree with thistof here when he says it's too smooth. It 's not all too smooth. What he's saying is that some thing which require impact shouldn't be eased out, but the whole movie isn't a punch or a person hitting a table.
So here's some tips I think you can use. Check out the 12 Principles of Animation and watch them and study them. (Not all of them apply to stop-motion but those are pretty obvious so don't study those). I'd say pacing is an important one especially. Sometimes you just need to not have any action. Sometimes you need more action. It's all about pacing and making things look realistic.
Next off, tie down your set and camera. It moved a lot in the video. The camera and set should NEVER move unless you're intentionally making it move. So try to keep it still.
Finally, I noticed that some motions paused to allow other things to move. For example, at around 6 seconds in, the guy moving his hand up stops moving when the crocodile guy moves. Keep an eye on motions and make sure they're completed and don't pause unnaturally. Remember, you can animate more than one thing in a frame at a time (even though it can be hard!).
Anyway, good job for your second animation! I think you'll improve quickly.
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